Safe Haskell	Safe-Inferred
Language	Haskell98

Options.Applicative.Builder

Contents

Parser builders
Modifiers
Readers
Builder for ParserInfo
Builder for ParserPrefs
Types

Synopsis

Parser builders

This module contains utility functions and combinators to create parsers for individual options.

Each parser builder takes an option modifier. A modifier can be created by composing the basic modifiers provided by this module using the Monoid operations mempty and mappend, or their aliases idm and <>.

For example:

out = strOption
    ( long "output"
   <> short 'o'
   <> metavar "FILENAME" )

creates a parser for an option called "output".

subparser :: Mod CommandFields a -> Parser a Source

Builder for a command parser. The command modifier can be used to specify individual commands.

strArgument :: Mod ArgumentFields String -> Parser String Source

Builder for a String argument.

argument :: ReadM a -> Mod ArgumentFields a -> Parser a Source

Builder for an argument parser.

flag Source

Arguments

:: a	default value
-> a	active value
-> Mod FlagFields a	option modifier
-> Parser a

Builder for a flag parser.

A flag that switches from a "default value" to an "active value" when encountered. For a simple boolean value, use switch instead.

flag' Source

Arguments

:: a	active value
-> Mod FlagFields a	option modifier
-> Parser a

Builder for a flag parser without a default value.

Same as flag, but with no default value. In particular, this flag will never parse successfully by itself.

It still makes sense to use it as part of a composite parser. For example

length <$> many (flag' () (short 't'))

is a parser that counts the number of "-t" arguments on the command line.

switch :: Mod FlagFields Bool -> Parser Bool Source

Builder for a boolean flag.

switch = flag False True

abortOption :: ParseError -> Mod OptionFields (a -> a) -> Parser (a -> a) Source

An option that always fails.

When this option is encountered, the option parser immediately aborts with the given parse error. If you simply want to output a message, use infoOption instead.

infoOption :: String -> Mod OptionFields (a -> a) -> Parser (a -> a) Source

An option that always fails and displays a message.

strOption :: Mod OptionFields String -> Parser String Source

Builder for an option taking a String argument.

option :: ReadM a -> Mod OptionFields a -> Parser a Source

Builder for an option using the given reader.

nullOption :: ReadM a -> Mod OptionFields a -> Parser a Source

Deprecated: Use option instead

Same as option.

Modifiers

short :: HasName f => Char -> Mod f a Source

Specify a short name for an option.

long :: HasName f => String -> Mod f a Source

Specify a long name for an option.

help :: String -> Mod f a Source

Specify the help text for an option.

helpDoc :: Maybe Doc -> Mod f a Source

Specify the help text for an option as a Doc value.

value :: HasValue f => a -> Mod f a Source

Specify a default value for an option.

Note: Because this modifier means the parser will never fail, do not use it with combinators such as some or many, as these combinators continue until a failure occurs. Careless use will thus result in a hang.

showDefaultWith :: (a -> String) -> Mod f a Source

Specify a function to show the default value for an option.

showDefault :: Show a => Mod f a Source

Show the default value for this option using its Show instance.

metavar :: HasMetavar f => String -> Mod f a Source

Specify a metavariable for the argument.

Metavariables have no effect on the actual parser, and only serve to specify the symbolic name for an argument to be displayed in the help text.

eitherReader :: (String -> Either String a) -> ReadM a Source

Convert a function in the Either monad to a reader.

noArgError :: ParseError -> Mod OptionFields a Source

Specify the error to display when no argument is provided to this option.

data ParseError Source

Constructors

ErrorMsg String
InfoMsg String
ShowHelpText
UnknownError
MissingError (OptTree (Chunk Doc))

Instances

Show ParseError
Monoid ParseError

hidden :: Mod f a Source

Hide this option from the brief description.

internal :: Mod f a Source

Hide this option from the help text

command :: String -> ParserInfo a -> Mod CommandFields a Source

Add a command to a subparser option.

completeWith :: HasCompleter f => [String] -> Mod f a Source

Add a list of possible completion values.

action :: HasCompleter f => String -> Mod f a Source

Add a bash completion action. Common actions include file and directory. See http://www.gnu.org/software/bash/manual/html_node/Programmable-Completion-Builtins.html#Programmable-Completion-Builtins for a complete list.

completer :: HasCompleter f => Completer -> Mod f a Source

Add a completer to an argument.

A completer is a function String -> IO String which, given a partial argument, returns all possible completions for that argument.

idm :: Monoid m => m Source

Trivial option modifier.

(<>) :: Monoid m => m -> m -> m infixr 6

An infix synonym for mappend.

Since: 4.5.0.0

mappend :: Monoid a => a -> a -> a

An associative operation

Readers

A collection of basic Option readers.

auto :: Read a => ReadM a Source

Option reader based on the Read type class.

str :: ReadM String Source

String Option reader.

disabled :: ReadM a Source

Null Option reader. All arguments will fail validation.

readerAbort :: ParseError -> ReadM a Source

Abort option reader by exiting with a ParseError.

readerError :: String -> ReadM a Source

Abort option reader by exiting with an error message.

Builder for `ParserInfo`

data InfoMod a Source

Modifier for ParserInfo.

Instances

Monoid (InfoMod a)

fullDesc :: InfoMod a Source

Show a full description in the help text of this parser.

briefDesc :: InfoMod a Source

Only show a brief description in the help text of this parser.

header :: String -> InfoMod a Source

Specify a header for this parser.

headerDoc :: Maybe Doc -> InfoMod a Source

Specify a header for this parser as a Doc value.

footer :: String -> InfoMod a Source

Specify a footer for this parser.

footerDoc :: Maybe Doc -> InfoMod a Source

Specify a footer for this parser as a Doc value.

progDesc :: String -> InfoMod a Source

Specify a short program description.

progDescDoc :: Maybe Doc -> InfoMod a Source

Specify a short program description as a Doc value.

failureCode :: Int -> InfoMod a Source

Specify an exit code if a parse error occurs.

noIntersperse :: InfoMod a Source

Disable parsing of regular options after arguments

info :: Parser a -> InfoMod a -> ParserInfo a Source

Create a ParserInfo given a Parser and a modifier.

Builder for `ParserPrefs`

data PrefsMod Source

Instances

Monoid PrefsMod

multiSuffix :: String -> PrefsMod Source

disambiguate :: PrefsMod Source

showHelpOnError :: PrefsMod Source

noBacktrack :: PrefsMod Source

columns :: Int -> PrefsMod Source

prefs :: PrefsMod -> ParserPrefs Source

defaultPrefs :: ParserPrefs Source

Default preferences.

Types

data Mod f a Source

An option modifier.

Option modifiers are values that represent a modification of the properties of an option.

The type parameter a is the return type of the option, while f is a record containing its properties (e.g. OptionFields for regular options, FlagFields for flags, etc...).

An option modifier consists of 3 elements:

A field modifier, of the form f a -> f a. These are essentially (compositions of) setters for some of the properties supported by f.
An optional default value and function to display it.
A property modifier, of the form OptProperties -> OptProperties. This is just like the field modifier, but for properties applicable to any option.

Modifiers are instances of Monoid, and can be composed as such.

You rarely need to deal with modifiers directly, as most of the times it is sufficient to pass them to builders (such as strOption or flag) to create options (see Builder).

Instances

Monoid (Mod f a)

data ReadM a Source

A newtype over 'ReaderT String Except', used by option readers.

Instances